LastLaunchAdadapter memory leaks

[obrienben]

Hi, just curious if you could offer any insight into a problem I am having. I'm using the heritrix3-wrapper library in an application running in Tomcat (v8) and frequently seeing the following message when shutting down the container, sometimes the message will show multiple times

05-Sep-2017 18:54:50.611 SEVERE [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.checkThreadLocalMapForLeaks The web application [h3-tester] created a ThreadLocal with key of type [org.netarchivesuite.heritrix3wrapper.jaxb.DateFormatLastLaunch$1] (value [org.netarchivesuite.heritrix3wrapper.jaxb.DateFormatLastLaunch$1@8245ae8]) and a value of type [org.netarchivesuite.heritrix3wrapper.jaxb.DateFormatLastLaunch] (value [org.netarchivesuite.heritrix3wrapper.jaxb.DateFormatLastLaunch@acc3985]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.

I am having some memory leak problems and I'm wondering if this is a cause or just a red herring.
I can see the use of ThreadLocal in the DateFormatLastLaunch class and the line explaining its use, because DateFormat is not threadsafe.
I realize NAS isn't a Tomcat application, but still wondering if you have experienced any similar messages about threads and this class?

Thanks,
Ben

[nclarkekb]

Generally speak ThreadLocal variables should not provide considerable leaks.
There should only be once variable per Thread. And thread local variables should automatically be garbage collected once the associated thread is stopped. Unless there is a reference to the object still alive.
We have similar warning in our projects which we have until now dismissed.

However to help find your memory leak I can probably give you a small program I wrote for this purpose. It attaches to a java process running in debug mode and dumps a list of all instances in the target jvm and how many instances there are. This way at least you can see which class/objects accumulate over this. I just need to polish it a little.

[obrienben]

Yea it did seem unlikely, good to know you have also seen the messages.
Thanks that would help a lot. Have you been running the heritrix3-wrapper under Java 7 or 8?